Na⁺, K⁺-ATPase inhibitors down-regulate gene expression of the intracellular signaling protein 14-3-3 in rat lens

To identify genes that are differentially expressed by Na⁺, K⁺-ATPase inhibitors, we used the differential display technique to compare mRNA expression patterns in rat lens. Lenses were treated with 10 μM ouabain, bufalin, or 19-norbufalin derivative for 24 h and were compared with control lenses. Differential display analysis revealed that one of the down-regulated genes was 14-3-3 0. Down-regulation was confirmed by Northern blot and by reverse transcription-polymerase chain reaction analysis. Reverse transcription-polymerase chain reaction of additional 14-3-3 isoforms revealed that the η and γ isoforms of 14-3-3 are also down-regulated by ouabain, bufalin, and 19-norbufalin derivative, whereas the zeta isoform is down-regulated only by bufalin. Down-regulation of the 14-3-3 isoforms occurred without a significant change in γ-crystallin gene expression. These results demonstrate that one of the consequences of Na⁺, K⁺-ATPase inhibition by exogenous or endogenous inhibitors is the down-regulation of mRNA transcripts encoding several isoforms of 14-3-3. Because the 143-3 proteins are multifunctional regulatory proteins, the reduction in the abundance of various isoforms will have profound effects on cell function.